Method of forming feedthrough with integrated brazeless ferrule

ABSTRACT

One aspect provides a method of forming a feedthrough device for an implantable medical device. The method includes providing a bulk insulator having a longitudinal length extending between first and second end faces, and including one or more conducting elements extending therethrough between the first and second end faces, the bulk insulator having a perimeter surface along the longitudinal length, and depositing one of a metal, metal alloy, or cermet on the perimeter surface to form a ferrule directly thereon, wherein the ferrule can be joined to other components of the implantable medical device.

BACKGROUND

Implantable medical devices, such as cardiac pacemakers ordefibrillators, typically include a metal housing having a feedthroughdevice (often referred to simply as a feedthrough) which establisheselectrical connections between a hermetically sealed interior of themetal housing and an exterior of the medical device. Feedthroughstypically include an insulator and a frame-like metal ferrule disposedabout a perimeter edge of the insulator. The ferrule is configured tofit into a corresponding opening in the metal housing, with the ferruletypically being welded to the housing to ensure a hermetic seal withrespect to the interior of the housing. Electrical conductors or“feedthrough pins” extend through the insulator to provide electricalpathways between the hermetically sealed interior of the housing and anexterior of the medical device. The insulator electrically isolates thefeedthrough pins from one another and from the metal ferrule andhousing.

The ferrule and insulator are typically joined to one another via abrazing or soldering process. Forming the metal ferrule (typically via amachining process) to meet the tight tolerances required to maintain adesired gap (about 10-50 μm) between the ferrule and insulator that isnecessary to achieve a quality braze joint is difficult. Additionally,if the gap is not maintained during the brazing process or if thebrazing itself is not properly performed, a weak joint may be formedbetween the ferrule and the insulator that may lead to premature failureof the implantable device.

For these and other reasons there is a need for the embodiments of thepresent disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIGS. 1A and 1B illustrate a feedthrough device in accordance with theprior art.

FIG. 2A illustrates a cross-sectional view of a feedthrough assembly inan implantable medical device in accordance with one embodiment.

FIG. 2B illustrates a cross-sectional view of a feedthrough assembly inan implantable medical device in accordance with one embodiment.

FIG. 3 illustrates a cross-sectional view of a feedthrough assembly inan implantable medical device in accordance with one embodiment.

FIG. 4 illustrates a method of forming a feedthrough device inaccordance with one embodiment.

FIG. 5 illustrates a method of segmenting a length of a bulk feedthroughdevice into a plurality of individual feedthroughs in accordance withone embodiment.

FIG. 6 illustrates a method of forming a feedthrough device inaccordance with one embodiment.

FIG. 7 is a flow diagram illustrating a method of forming a feedthroughassembly in accordance with one embodiment.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is to be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

In accordance with one embodiment of the present disclosure, a method offorming a feedthrough device for an implantable medical device isprovided. A bulk insulator having a longitudinal length extendingbetween first and second end faces is provided, the bulk insulatorincluding one or more conducting elements extending therethrough betweenthe first and second end faces, and having a perimeter surface along thelongitudinal length. A metal, metal alloy, or cermet is deposited on theperimeter surface to form a ferrule directly on the perimeter surface ofthe bulk insulator. After the metal, metal alloy, or cermet has beendeposited, the bulk insulator is segmented along the longitudinal lengthinto individual segments each having a thickness, with each individualsegment forming a feedthrough device.

According to one embodiment, the perimeter surface of the bulk insulatoris metallized with a metallization layer prior to depositing the metal,metal alloy, or cermet. In one embodiment, the metallization layer is ofa metal selected from a group consisting of titanium, niobium, platinum,palladium, and gold, and has a thickness in a range from 0.2 μm to 10μm.

Embodiments described herein for depositing a metal, metal alloy, orcermet on the insulator to form a ferrule directly on the perimetersurface thereof provides advantages over known processes. Depositing themetal ferrule directly on the insulator, or on a metallized layerthereon, eliminates braze and solder joints which exist between theferrule and insulator of conventional ferrules, thereby providing astronger and more reliable hermetic seal there between. Depositing theferrule directly on the insulator also eliminates the costly and timeconsuming process of first machining ferrules to the tight tolerancesrequired to provide a proper gap between the insulator and ferrulenecessary to produce quality brazing and solder joints. It alsoeliminates the necessity of maintaining such gap as required to ensurequality joints during the brazing and soldering process itself, therebyresulting in stronger and more consistent hermetic seals between theferrule and insulator.

According to one embodiment, the metal, metal alloy, or cermet isdeposited using a suitable powder deposition process. In one embodiment,the powder deposition process comprises a Laser Engineered Net Shaping™process to coat the perimeter surface of the insulator with the metal,metal alloy, or cermet. In one embodiment, the powder deposition processcomprises a plasma thermal spraying process to coat the perimetersurface of the insulator. In one embodiment, the metal or metal alloy isdeposited with a thickness in a range from 200 μm to 800 μm. In oneembodiment, the metal or metal alloy forming the ferrule comprises oneof a group consisting of niobium, titanium, titanium alloy, tantalum,tungsten, molybdenum, cobalt, zirconium, chromium, platinum, and alloycombinations thereof. In one embodiment, the cermet comprises acombination of a ceramic, such as aluminum oxide (Al₂O₃) and Zirconiumdioxide (ZrO₂), for example, and a metal, such as Niobium, Molybdenum,titanium, cobalt, zirconium, chromium, platinum, tantalum, and iridium,for example.

In one embodiment, machining is performed after deposition of the metal,metal alloy, or cermet on the perimeter surface of the insulator toprovide the ferrule with a desired final cross-sectional shape. In oneembodiment, deposition of the metal, metal alloy, or cermet is finelycontrolled so that the resulting ferrule has a desired finalcross-sectional shape. Controlling deposition of the metal, metal alloy,or cermet in this fashion substantially reduces or eliminates the timeand expense required to machine conventional ferrules.

According to one embodiment, the insulator comprises aluminum oxide andthe conductive elements comprise a cermet. Using cermet conductiveelements also eliminates braze and/or solder joints between theconductive elements and the insulator and such that the entire ferruleis brazless/solderless.

In one embodiment, the insulator is preheated using a laser to a desiredtemperature within a range from 800 to 1500° C. prior to depositing themetal, metal alloy, or cermet on the perimeter surface. According to oneembodiment, the insulator is preheated to the desired temperature in atime period ranging from 15 to 180 seconds. In one embodiment, the laseris used to ramp down a temperature of the insulator after deposition ofthe metal, metal alloy, or cermet thereon. Controlling the temperatureof the insulator in this fashion reduces or eliminates the potential forcracking of the insulator that might otherwise result from a thermalshock during the deposition process.

Another aspect provides a method of forming a feedthrough device for animplantable medical device including providing an insulator having oneor more conducting elements extending therethrough, the insulator havinga perimeter edge surface, metallizing the perimeter edge surface toprovide a metallized layer thereon, and depositing a metal, metal alloy,or cermet having a thickness in a range from 200 to 800 μm on themetallized layer to form a ferrule thereon and thereby form thefeedthrough device. According to one embodiment, such method providesdepositing the metal, metal alloy, or cermet on individual feedthroughdevices in lieu of forming such devices from a bulk insulator.

Such method provides several of the advantages discussed above,including forming stronger and more consistent and uniform hermeticseals between ferrules and insulators relative to conventional solderand braze joints, and the elimination of the formation and maintenanceof a high-tolerance gap between the ferrule and insulator which isrequired for producing convention solder and braze joints.

One embodiment provides a feedthrough for an implantable medical deviceincluding a ferrule comprising a metal, metal alloy, or cermet that isconfigured to be jointed to a case of the implantable device, aninsulator substantially surrounded by the ferrule and sharing aninterface therewith, the insulator comprising a glass or ceramicmaterial, and conductive elements formed through the insulator providingan electrically conductive path through the insulator. The feedthroughis characterized in that there is no braze, solder, or weld joint at theinterface between the ferrule and the insulator and that there is nobraze or solder at interfaces between the insulator and the conductiveelements. The complete absence of braze or solder joints whichcharacterizes such a feedthrough enables the feedthrough to provide animproved and more durable hermetic seal for an implantable medicaldevice in which it is employed.

FIGS. 1A and 1B respectively illustrate perspective and sectional viewsof a conventional feedthrough device 10, such as for an implantablemedical device. Feedthrough device 10 includes a ferrule 12, aninsulator 14 and feedthrough pins 16. Ferrule 12 is an annular,frame-like metal structure forming an interior opening in whichinsulator 14 is disposed. Feedthrough pins 16 extend through insulator14, with insulator 14 serving to electrically insulate feedthrough pins16 from one another and from ferrule 12.

Ferrule 12 is configured to fit into a corresponding opening of a metalcase for an implantable medical device. Typically, ferrule 12 is weldedto the metal case so that it is tightly secured thereto and to ensure ahermetic seal with respect to an interior space of the medical devicedefined by the metal case. Feedthrough pins 16 extending throughinsulator 14 provide electrical connection from the interior to theexterior of the metal case while maintaining a hermetic seal. Flanges 15are sometimes provided on ferrule 12 to further aid in securingfeedthrough device 10 to the opening of the case of the implantablemedical device and ensuring ifs hermetic seal.

Typically, ferrule 12 is a bio-compatible metal, such as titanium orniobium, while insulator 14 is a ceramic or glass material. Whencoupling insulator 14 to ferrule 12, a perimeter edge of insulator 14 istypically metalized (i.e. a metal coating is applied, such as bysputtering, for example) to provide a thin metal coating 20 thereon, andinsulator 14 is placed within the interior opening defined by ferrule12. A brazing process, using a brazing material 22, such as gold, isthen carried to join ferrule 12 to insulator 14 via metal coating 20.Similarly, a braze 18 is often used to couple feedthrough pins 16 toinsulator 14.

In order to achieve a quality braze between ferrule 12 and insulator 14,a proper gap needs to be maintained between ferrule 12 and insulator 14,typically about 10-50 μm, so that capillary action will properly drawbrazing material 22 into the gap to create a strong and reliablehermetic seal. Forming ferrule 12, typically via machining processes, tomeet the tight tolerances required to provide the desired gap betweenthe ferrule 12 and insulator 14, as well as to the dimensions of theopening in the metal case, can be difficult. If the gap between theferrule 12 and insulator 14 is too small, the brazing material 22 maynot be adequately drawn into the gap, resulting in a weak joint. Also,during the brazing process, intermetallics are always formed between thebrazing material 22 and ferrule 12, with the intermetallics beingbrittle as compared to the brazing material 22. If the gap is too small,the amount of intermetallics may be large relative to the amount ofbrazing material 22, resulting in a brittle joint that can crack andcompromise the hermetic seal.

FIG. 2A is cross-sectional view illustrating a feedthrough device 110according to one embodiment of the present disclosure. Feedthroughdevice 110 includes a ferrule 112, an insulator 114, and conductingelements 116, with insulator 114 having a perimeter edge surface orperimeter surface 115 extending between a first or upper major surface117 a and a second or lower major surface 117 b. According toembodiments described herein, ferrule 112 is formed from one of a metal,metal alloy, or cermet. Feedthrough device 110 is characterized,relative to conventional feedthrough devices, by the absence of ametallization layer and a braze material (such as metallization layer 20and braze material 22 of FIG. 1B, for example) between the material offerrule 112 and the glass or ceramic material of insulator 114. Instead,according to embodiments of the present disclosure, the metal of ferrule112 is deposited directly on the material of insulator 114 on perimeter115, using deposition techniques which will be discussed in greaterdetail below, to form a hermetic seal therebetween without the use ofbraze or solder.

Ferrule 112 can be formed using the deposition techniques to have avariety of shapes and cross-sections. According to one embodiment, asillustrated by FIG. 2, ferrule 112 is formed with a flange 130 extendinglaterally along an upper surface 132, resulting in a notch 134 along alower surface 136, giving ferrule 112 a stepped, rectangular shape incross-section. According to one embodiment, a desired final shape offerrule 112 is achieved directly via the deposition process. In oneembodiment, machining is performed after initial deposition of the metalof ferrule 112 to achieve the desired final shape of ferrule 112.

According to one embodiment, as illustrated by FIG. 2A, insulator 114and conducting elements 116 are formed in a first process such thatinterfaces between insulator 114 and conducting elements 116 are alsohermetically sealed without the use of a braze or solder. According toone example of such an embodiment, insulator 114 is a ceramic material,such as aluminum oxide (Al₂O₃), and conducting elements 116 are a cermetmaterial.

In the context of one embodiment, the terms, “cermet” or“cermet-containing,” refers composite materials made of ceramicmaterials in a metallic matrix (binding agent). These are characterizedby their particularly high hardness and wear resistance. The “cermets”and/or “cermet-containing” substances are cutting materials that arerelated to hard metals, but contain no tungsten carbide hard metal andare produced by powder metallurgical means. A sintering process forcermets and/or cermet-containing elements is the same as that forhomogeneous powders, except that the metal is compacted more strongly atthe same pressuring force as compared to the ceramic material. Thecermet-containing bearing element has a higher thermal shock andoxidation resistance than sintered hard metals. According to oneembodiment, the ceramic components of the cermet are aluminum oxide(Al₂O₃) and zirconium dioxide (ZrO₂), for example, and niobium,molybdenum, titanium, cobalt, zirconium, chromium, and platinum, forexample, may be employed as the metallic components.

According to one embodiment, the ceramic of insulator 114 of FIG. 2A isa multi-layer ceramic sheet into which a plurality of vias isintroduced. The cermet of conducting elements 116 is then introducedinto the vias. In one embodiment, both materials are introduced in agreen state, and the combination is fired together. Accordingly, thejoining of the insulator 114 and conducting elements 116 forms ahermetic seal therebetween without the use of braze or solder.

FIG. 2B is a cross-sectional view of feedthrough device 110 of FIG. 2A,but further includes a metallized layer 138 disposed on the perimetersurface 115 of ceramic insulator 114 at the interface between insulator114 and the material of ferrule 112. According to one embodiment,metallized layer 138 is disposed on insulator 114 via a sputter coatingprocess. According to one embodiment, metallized layer 138 is disposedon insulator 114 via an electroplating process. According to oneembodiment, metallized layer 138 comprises a bio-compatible metal, suchas Niobium, Platinum, Palladium, Titanium, and Gold, for example. In oneembodiment, metallized layer 138 is deposited so as to have a thicknessin a range from 0.2 to 10 μm. As will be described in greater detailbelow, after deposition of metallized layer 138 on insulator 114, ametal, metal alloy, or cermet is deposited on and built-up on metallizedlayer 138 to form ferrule 112.

FIG. 3 is a cross-sectional view illustrating portions of an implantablemedical device 140 having a metal case 142 in which feedthrough device110 of FIG. 2A is installed. In one embodiment, feedthrough device 110is positioned within an opening in metal case 142, and ferrule 112 islaser welded to metal case 142 such that an interior 144 of metal case142 is hermetically sealed relative to its exterior 146.

By forming insulator 114 and conducting elements 116 using a cermetmaterial, as described above, and by depositing the metal of ferrule 112directly on a perimeter surface of insulator 114, a ferrule formedaccording to embodiments of the present application, such as ferrule 112of FIG. 2A, provides hermetic seals between ferrule 112 and insulator114, and between insulator 114 and conducting elements 116 without theuse of braze or solder. As such, a feedthrough device according to thepresent disclosure, such as feedthrough device 110 of FIG. 2A,eliminates shortcomings associated with the braze and/or solder jointsof conventional feedthrough devices (such as illustrated by FIGS. 1A and1B, for example), and provides a more reliable hermetic seal between aninterior and exterior of an implantable device, such as between theinterior 144 and exterior 146 of implantable medical device 140.

According to embodiments, a suitable deposition process, includingsuitable powder deposition processes, is employed to deposit thematerial forming ferrule 112 (e.g. metal, metal alloy, cermet) directlyon insulator 114. Examples of such deposition processes include powderdeposition processes such as Laser Engineered Net Shaping™ and plasmathermal spraying, for example.

FIG. 4 is a block and schematic diagram generally illustrating oneembodiment of a Laser Engineered Net Shaping™ (LENS®) process fordepositing a metal, metal alloy, or cermet on insulator 114 to formferrule 112. The LENS process employs a high power laser 150, a powderdelivery system 152, a deposition or print head 154, and a translationtable 156.

According to one embodiment, a bulk insulator 114 a having a length “L”between first and second end surfaces 115 a, 115 b, and one or moreconducive elements extending through insulator 114 a from first endsurface 115 a to a second end surface 115 b, such as conductive elements116 a and 116 b, is mounted on translation table 156. According to oneembodiment, bulk insulator 114 a has been previously formed, such as bythe cermet process described above, so that conductive elements 116 aand 116 b comprise cermet and a brazeless/solderless hermetic sealexists between conductive elements 116 a and 116 b. According to oneembodiment, bulk insulator 114 includes a metallization layer 138 adisposed on its external circumferential surface, such as via asputtering process or electroplating process as described above.Although illustrated in FIG. 4 as having a circular cross-section, bulkinsulator 114 a can have a variety of cross-sectional shapes, such asrectangular or oval, for example.

During the deposition process, laser 150 provides a high power laserbeam 160 which travels through the center of deposition head 154 and isfocused to a point on the surface of bulk insulator 114 a by one or morelenses 162. Powder delivery system 152 provides a fine powder 164 of ametal, metal alloy, or cermet components to a plenum 166 about thecircumference of deposition head 154. The fine powder 164 is coaxiallyinjected into the focused high power laser beam 160 a at an outlet 168of deposition head 154. Powder 164 can be circumferentially injectedinto focused laser beam 160 a by gravity or by using a pressurizedcarrier gas. The powder 164 is sintered by focused laser beam 160 a anddeposited on the surface of bulk insulator 114 a, or onto metallizedlayer 138 a when present, such as illustrated by the exemplaryembodiments of FIGS. 2A and 2B.

According to one embodiment, powdered metals used to form ferrule 112include Ti (Titanium), Ti6Al4V (Titanium Alloy), Nb (Niobium), Ta(Tantalum), W (Tungsten), or alloy combinations of these, for example.According to one embodiment, cermet powder includes a ceramic component,such as Aluminum Oxide (Al2O3) and Zirconium dioxide (ZrO2), forexample, and a metal component such as Niobium, Molybdenum, titanium,cobalt, zirconium, chromium, platinum, tantalum, and iridium, forexample. According to one embodiment, combinations of these componentsforms the cermet powder which is laser sintered onto insulator 114 a.

According to one embodiment, lasers used for laser 150 include Nd:YAG,Fiber, and CO2, for example. According to one embodiment, Nd: YAG andFiber are employed due to their approximately 1 μm wavelength having ahigher optical absorption into the metals.

As the melted/sintered powder 164 is deposited onto the surface of bulkinsulator 114 (or onto metallization layer 138 a if present),translation table 156 is controlled so as to rotate bulk insulator 114 aabout the x-axis and to translate bulk insulator 114 a along the x-axisto deposit melted/sintered powder 164 in a desired fashion on thecircumferential surface of bulk insulator 114 a and thereby form ferrule112. Melted/sintered powder 164 is deposited in a series of layers tobuild the deposited metal up to a desired thickness to form ferrule 112.According to one embodiment, translation table 156 also controlsmovement of bulk insulator 114 a along the z-axis as the thickness ofthe material deposited on bulk insulator 114 a increases. In otherembodiments, a position of deposition head 154 along the z-axis can becontrolled.

According to one embodiment, deposition of the metal, metal alloy, orcermet onto bulk insulator 114 a is precisely controlled so that themetal, metal alloy, or cermet is built-up and directly deposited withthe desired final shape of ferrule 112, such as the rectangular, steppedshape of ferrule 112 of FIG. 2A, without a need for post-depositionmachining. According to one embodiment, the metal, metal alloy, orcermet is deposited on bulk insulator 114 in a range from 200 μm to 800μm to form ferrule 112. In one embodiment, an inert gas 170 is suppliedto deposition head 154 to shield the metal or metal alloy from oxygen,thereby suppressing oxidation of the metal or metal alloy, and so thatthe metal or metal alloy sinters properly and can be controlled moreaccurately. According to one embodiment, mechanical machining isperformed after the initial deposition of the metal, metal alloy, orcermet on bulk insulator 114 a to achieve the desired final shape offerrule 112.

In one embodiment, an additional laserl 80 is used to preheat thematerial of bulk insulator 114 a to reduce the thermal shock from laser150 during the deposition process and thereby reduce the chance ofcracking of the ceramic material of bulk insulator 114 a duringdeposition. According to one embodiment, laser 180 is configured to scanthe surface of insulator 114 to raise the temperature of bulk insulator114 a from room temperature to a temperature of 800-1,500° C. In oneembodiment, laser 180 is a CO₂ laser. According to one embodiment, laser180 using a ramp rate of 15-180 seconds to heat bulk insulator 114 afrom room temperature to the desired preheat temperature. According toone embodiment, laser 180 is similarly used to carry out a cool downprocess to ramp the temperature down to room temperature afterdeposition of the metal of ferrule 112.

In one embodiment, the preheating of bulk insulator 114 a, thedeposition of the metal, metal alloy, or cermet onto the surface of bulkinsulator 114 a to form ferrule 112, and the subsequent cool downprocess is carried out in a vacuum or in an inert environment (e.g.argon) to keep the metal or metal alloy from being oxidized.

As illustrated by FIG. 5, according to one embodiment, after completingthe deposition of the material forming ferrule 112 on the length “L” ofbulk insulator 114 a to form a resulting length “L” of a bulkfeedthrough device 110 a, the bulk feedthrough device 110 a is cut intosegments to form multiple individual feedthrough devices 110 (such asillustrated by FIGS. 2A and 2B), each having a desired thickness “Th”.According to one embodiment, the length “L” of bulk feedthrough device110 a is segmented using a saw 182.

In other embodiments, not illustrated herein, in lieu of performing thedeposition of the material of ferrule 112 on bulk insulators (such asbulk insulator 114 a), individual insulators 114 having one or moreconducting elements 116 extending therethrough are coated with themetal, metal alloy, or cermet, such as by the above described process ofFIG. 4, to form individual feedthrough devices 110.

FIG. 6 is a block and schematic diagram generally illustrating oneembodiment of a process for depositing material directly on bulkinsulator 114 a (or on individual insulators 114) to form ferrule 112.The process illustrated by FIG. 5 is commonly referred to as plasmathermal spraying, and employs a chamber 190 in which a plasma gun 192 isdisposed. Plasma gun 192 includes a body 194 having a conical cavity 196in which a cathode 198 is disposed and forms an annular cavity 200 thereabout. A low-pressure, inert gas atmosphere is created within aninterior of chamber 190 (e.g. argon, an argon-helium mixture, or anargon-hydrogen mixtures, for example).

During a coating process, a power supply 204 is energized to create anarc 206 between 194 and cathode 198 in annular passage 200. A plasmagas, such as a mixture of argon and helium, for example, is flowedthrough annular passage 200 and a high temperature, high velocity plasmagas stream 210 is expelled via nozzle 212. A powder injection system 214injects a fine powder 216 of a metal, metal alloy, or cermet componentswhich is entrained in the plasma gas stream 210, and which aresubsequently melted and deposited on the surface of bulk insulator 114 ato form ferrule 112. Materials similar to those described above withrespect to the LENS process of FIG. 4 may be employed for the metal,metal alloys, and cermet. As also described above with regard to theLENS process of FIG. 4, a translation table 218 rotates bulk insulator114 a about the x-axis and controls lateral movement of bulk insulator114 a along the x-axis so as to deposit the materials forming ferrule114 in a desired fashion on the outer diameter of the ceramic materialof bulk insulator 114 a.

Similar to that described above with respect to the LENS process of FIG.4, according to one embodiment, deposition of the metal, metal alloy, orcermet onto bulk insulator 114 a (or onto metallized layer 138 whenpresent) is precisely controlled so that the material is built-up anddirectly deposited with the desired final shape of ferrule 112, such asthe rectangular, stepped shape of ferrule 112 of FIG. 2A, without theneed for post-deposition machining. According to one embodiment, themetal, metal alloy, or cermet is deposited on bulk insulator 114 a in arange from 200 μm to 800 μm to form ferrule 112. In other embodiments,post-deposition machining is performed to achieve a desired final shapeof ferrule 112.

According to one embodiment, a laser 220 is employed to carry outpreheating and cool down processes similar to LENS process describedabove by FIG. 4. Also, as described above by FIG. 5, after deposition offerrule 112 onto bulk insulator 114 a by the plasma thermal sprayingprocess of FIG. 6, the resulting bulk feedthrough device 110 a issegmented to individual feedthrough devices 110, such as illustrated byFIGS. 2A and 2B, for example.

FIG. 7 is a flow diagram illustrating a process 250 of forming afeedthrough device in accordance with one embodiment. Process 250 beginsat 252 with receiving an insulator having one or more conductingelements extending therethrough. According to one embodiment, theinsulator is one such as insulator 114 of FIG. 2A, wherein conductingelements 116 are of a cermet material such that there is no braze orsolder at interfaces between conductive elements 116 and the material ofinsulator 114, such as a glass or ceramic material. According to oneembodiment, the insulator is a bulk insulator, such as bulk insulator114 a illustrated by FIG. 4, which has a length “L” between opposing endfaces, with cermet conducting elements extending between the opposingfaces. According to one embodiment, the insulator has a circular or ovalcross-section, for example, but can have any number of cross-sectionalshapes.

According to one embodiment, after receiving the insulator, theinsulator is optionally metallized to form a metallization layer aboutan exterior edge surface of the insulator, such as metallization layer138 about a perimeter edge surface 115 of insulator 114 as illustratedby the embodiment of FIG. 2A.

At 258, a material, such as a metal, metal alloy, or cermet, forexample, for forming a ferrule, such as ferrule 112 of the embodiment offeedthrough 110 illustrated by FIG. 2A, is deposited on a perimetersurface of the insulator. According to one embodiment, the materialforming ferrule 112 is deposited using a LENS® process, such asgenerally illustrated and described by FIG. 4. According to oneembodiment, the material forming ferrule 112 is deposited using a plasmathermal spraying process, such as generally illustrated and described byFIG. 6. According to one embodiment, the process for deposition of thematerial forming the ferrule is controlled to the extent that thematerial is deposited such that the ferrule is directly formed with adesired final shape (e.g. cross-sectional shape). In one embodiment, thematerial is deposited on individual insulators, such insulator 114 ofFIG. 2A. In one embodiment, the material is deposited on the perimetersurface of a bulk insulator, such as bulk insulator 114 a of FIG. 4, forexample.

Optionally, at 256, according to one embodiment, the perimeter surfaceof the insulator is preheated with a laser, for example, to a desiredtemperature prior to the deposition of metal at 258. Preheating theperimeter surface of the insulator, such as with laser 180 of FIG. 4,reduces the thermal shock to insulator 114 that might otherwise becaused by the material deposition process, and thereby reduces crackingof insulator 114 during the deposition process.

According to one embodiment, process 250 ends at 258. However, in oneembodiment, process 250 optionally includes, as indicated at 260,performing a controlled cool down of insulator 114 and the deposited(e.g. metal, metal alloy, cermet), such as via laser 180 of FIG. 4. Sucha controlled cool down further reduces the chances for thermally inducedcracking of the material of insulator 114 and improves the chances ofachieving a better bond between the deposited material forming ferrule112 and the ceramic or glass material, for example, of insulator 114.

Additionally, according to one embodiment, process 250 optionallyincludes, at 262 a machining process when the material of ferrule 112 isnot deposited so as to have a desired final shape. Such machiningprocess machines the “rough” deposition of the material ferrule 112,such as deposited by the processes of FIGS. 4 and 6, for example, to afinal desired shape.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of forming a feedthrough device for animplantable medical device, the method comprising: providing a bulkinsulator having a longitudinal length extending between first andsecond end faces, and including one or more conducting elementsextending therethrough between the first and second end faces, the bulkinsulator having a perimeter surface along the longitudinal length; anddepositing one of a metal, metal alloy, or cermet on the perimetersurface to form a ferrule directly thereon, wherein the ferrule can bejoined to other components of the implantable medical device.
 2. Themethod of claim 1, wherein the depositing of the metal, metal alloy, orcermet comprises a powder deposition process.
 3. The method of claim 2,wherein the powder deposition process comprises a Laser Engineered NetShaping™ process to coat the perimeter surface of the insulator with themetal, metal alloy, or cermet.
 4. The method of claim 2, wherein thepowder deposition process comprises a plasma thermal spraying process tocoat the perimeter surface of the insulator with the metal, metal alloy,or cermet.
 5. The method of claim 1, further including metallizing theperimeter surface to provide a metallized layer on the perimeter surfaceprior to depositing the metal, metal alloy, or cerment.
 6. The method ofclaim 5, wherein the metallized layer has a thickness in a range from0.2 μm to 10 μm.
 7. The method of claim 5, wherein the metallized layeris of a metal comprising one selected from a group consisting oftitanium, niobium, platinum, Palladium, and gold.
 8. The method of claim1, wherein after the metal, metal alloy, or cermet has been deposited,the method further includes segmenting the bulk insulator along thelongitudinal length into individual segments each having a thickness,each individual segment forming a feedthrough device.
 9. The method ofclaim 1, further including preheating the insulator with a laser to adesired temperature within a range from 800 to 1500° C. prior todepositing the metal or metal alloy on the perimeter surface.
 10. Themethod of claim 1, wherein the preheating from room temperature to thedesired temperature has a ramp rate from 15 to 180 seconds.
 11. Themethod of claim 1, further including using a laser to ramp down atemperature of the insulator from a temperature at a time of thedepositing of the metal or metal alloy to room temperature.
 12. Themethod of claim 1, wherein depositing the metal or metal alloy includescontrolling deposition of the metal or metal alloy so that the resultingferrule has a desired final cross-sectional shape.
 13. The method ofclaim 1, further including machining the metal or metal alloy depositedon the perimeter surface of the insulator to provide the ferrule with adesired final cross-sectional shape.
 14. The method of claim 1, whereinthe metal or metal alloy forming the ferrule comprises one of a groupconsisting of niobium, titanium, titanium alloy, tantalum, tungsten,molybdenum, cobalt, zirconium, chromium, platinum, and alloycombinations thereof.
 15. The method of claim 1, wherein the insulatorcomprises aluminum oxide and the conductive elements comprise a cermet.16. The method of claim 1, wherein depositing the metal or metal alloyincludes depositing the metal or metal alloy with a thickness in a rangefrom 200 μm to 800 μm.
 17. A method of forming a feedthrough device foran implantable medical device, the method comprising: providing aninsulator having one or more conducting elements extending therethrough,the insulator having a perimeter edge surface; metallizing the perimeteredge surface to provide a metallized layer thereon; and depositing oneof a metal, metal alloy, or cermet having a thickness in a range from200 to 800 μm on the metallized layer using a powder deposition processto form a ferrule thereon and thereby form the feedthrough device. 18.The method of claim 17, wherein the metallized layer has a thickness ina range from 0.2 μm to 10 μm and comprises a metal selected from a groupof metals consisting of titanium, niobium, platinum, Palladium, andgold.
 19. The method of claim 17, wherein the powder deposition processcomprises a Laser Engineered Net Shaping™ process.
 20. The method ofclaim 17, wherein the powder deposition process comprises a plasmathermal spraying process.
 21. A feedthrough for a medical implantabledevice comprising: a ferrule comprising a metal that is configured to bewelded to a case of the implantable device; an insulator substantiallysurrounded by the ferrule and sharing an interface therewith, theinsulator comprising a glass or ceramic material; conductive elementsformed through the insulator providing an electrically conductive paththrough the insulator; characterized in that there is no braze, solder,or weld joint at the interface between the ferrule and the insulator andthat there is no braze or solder at interfaces between the insulator andthe conductive elements.